<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <!-- vue.js 提供的插槽 -->
      <slot>

      </slot>
    </div>
    <div class="dots">
      <span class="dot" v-for="(item,index) in dots" :class="{active:currentPageIndex===index}"></span>
    </div>
  </div>

</template>

<script type="text/ecmascript-6">
  import BScroll from 'better-scroll'
  import {addClass} from "common/js/dom";

  export default {
    data() {
      return {
        dots: [],
        currentPageIndex:0
      }
    },
    props: {
      loop: {
        type: Boolean,
        default: true
      },
      autoPlay: {
        type: Boolean,
        default: true
      },
      interval: {
        type: Number,
        default: 4000
      }
    },
    mounted() {
      setTimeout(() => {
        this._setSliderWidth()
        this._initDots()
        this.initSlider()
        if (this.autoPlay){
          this._play()
        }
      }, 20)

      window.addEventListener('resize',() =>{
        if (!this.slider){
          return
        }
        this._setSliderWidth(true)
        this.slider.refresh()
      })

    },
    methods: {
      _play(){
        let pageIndex = this.currentPageIndex+1
        if (this.loop){
          pageIndex += 1
        }
        this.timer = setTimeout(()=>{
          this.slider.goToPage(pageIndex,0,400)
        },this.interval)
      },
      _initDots() {
        this.dots = new Array(this.children.length )

      },
      _setSliderWidth(isResize) {
        this.children = this.$refs.sliderGroup.children

        let width = 0
        let sliderWidth = this.$refs.slider.clientWidth
        for (let i = 0; i < this.children.length; i++) {
          let child = this.children[i]
          addClass(child, 'slider-item') // 动态为每个元素添加class
          child.style.width = sliderWidth + 'px'
          width += sliderWidth

        }

        if (this.loop&&!isResize ) {
          width += 2 * sliderWidth
        }

        this.$refs.sliderGroup.style.width = width + 'px'
      },
      initSlider() {
        this.slider = new BScroll(this.$refs.slider, {
          scrollX: true,
          scrollY: false,
          momentum: false,
          snap: true,
          snapLoop: this.loop,
          snapThreshold: 0.3,
          snapSpeed: 400

        })

        this.slider.on('scrollEnd',()=>{
          let pageIndex = this.slider.getCurrentPage().pageX

          if (this.loop){
            pageIndex-=1
          }

          this.currentPageIndex = pageIndex

          if (this.autoPlay){
            clearTimeout(this.timer)
            this._play()
          }
        })

      }
    },
    destroyed(){
      clearTimeout(this.timer)
    }
  }
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
  @import "~common/stylus/variable"

  .slider
    min-height: 1px
    .slider-group
      position: relative
      overflow: hidden
      white-space: nowrap
      .slider-item
        float: left
        box-sizing: border-box
        overflow: hidden
        text-align: center
        a
          display: block
          width: 100%
          overflow: hidden
          text-decoration: none
        img
          display: block
          width: 100%
    .dots
      position: absolute
      right: 0
      left: 0
      bottom: 12px
      text-align: center
      font-size: 0
      .dot
        display: inline-block
        margin: 0 4px
        width: 8px
        height: 8px
        border-radius: 50%
        background: $color-text-l
        &.active
          width: 20px
          border-radius: 5px
          background: $color-text-ll
</style>
